The "edit/move or copy/create copy" menu has stopped working within the
workbook I have significant amount of time invested. It won't duplicate a
worksheet within the workbook or to a new workbook.

Sometimes, this file gets so corrupted, excel stops responding and it cannot
be repaired. I have to revert to a saved copy and duplicate the changes
since the save.

I assume there is some registry damage. How do I fix this?